Container for packaging tacky materials



Aug. 27, 1957 J. s. BARTON ETAL 2,804,205

CONTAINER FOR PACKAGING TACKY MATERIALS Filed Nov. 21, 1955 PAPER BAG OR OTHER RELEASE COATING OF! WAX,ASPHALT, RUBBER BASE MEMBER. ACRYLIC POLYMER OR OTHER TACKY MATERIAL.

CHLOROPRENE POLYMER, ACRYLIC-BUTADIENE COPOLYMER, BUTADlENE-STYRENE COPOLYMER, ACRYLIC-BUTADIENE-VINYL TERPOLYMER, ACRYLIC, VINYL POLYMER MIXTURES OR ACRYLlC-BUTADIENE COPOLYMER, VINYL POLYMER MIXTURE INVENTORS JOHN s. BARTON WALLACE J. FOLLETTE BY FRED L. SCHMIDT TTY.

United States PatentO CONTAINER FOR PACKAGING TACKY MATERIALS John S. Barton, Wallace J. Follette, and Fred L. Schmidt, Camas, Wash assignors to Crown Zellerbach Corpo ration, San Francisco, Calif., a corporation of Nevada Application November 21, 1955, Serial No. 547,952

14 Claims. (Cl. 206-84) This invention relates to containers for tacky materials such as wax, asphalt, rubber and the like which normally are solid at room temperature. The invention pertains particularly to paper bags and other fibrous cellulosic containers adapted to be employed for the packaging of the aforesaid tacky materials.

The packaging of wax, asphalt, rubber and like tacky materials is made difficult by the tendency of these materials to adhere to the inner surfaces of the containers in which they are packaged. Where the containers comprise paper bags or other fibrous, cellulosic wrappers, the tacky contents of the package often becomes firmly bonded to'the adjacent fibrous surfaces.

As a result, when the container is stripped from its contents, portions of the container often remain behind firmly secured to the surface of the tacky material. This presents a problem, since for many uses the contents of the package must be free from contamination by the packaging material. Removal of the latter is a diflicult and time consuming operation, however, and results in substantial loss of time and increased expense.

Accordingly, the inner surface of a container which is suitable for packaging tacky materials of the class described herein, should be coated with a film which meets the following requirements:

' l. Releasability.The coating must be capable of rapid and clean release from the tacky material upon stripping the container therefrom.

' 2. Oil and grease resistance-The coating must possess good oil and grease resistance to prevent penetration of the packaged material through the container.

,This is particularly important when the tacky material is molten wax or asphalt.

3. Inertness to the tacky material.--The coating must be inert to the tacky substance to be packaged, so that no chemical or physical reaction occurs between them.

4. Bond to the inner wall of the conzainer.The coating must have the ability to form a strong bond to the .inner surface of the container, thereby preventing its partial or total delamination therefrom. If the bond is not suiiiciently strong, portions of the coating may be left on the surface of the tacky material when the package is opened. This would cause undesirable contamination of the material.

5. Other physical properties.-For best release from the package contents, the coating should be substantially 'dry, smooth and flexible at room temperature. Also, it

ployed for packaging tacky materials, but these in the majority of instances have been unsatisfactorybecause .the release coatings used have-not met one or more of 2,804,205 Patented Aug. 27, 1957 the foregoing requirements. Thus it is common practice to package wax and like materials in metal or fiber drums. However, removal of the wax from the drums usually requires a preliminary melting of the wax, which, in turn, incurs a substantial cost for labor and for heating and handling equipment.

Similarly, wax and like materials conventionally are formed into slabs which then are wrapped individually in paper sheets or placed in cartons. However, the formation of such slabs is an expensive operation, and use of this technique often results in the undesirable adhesion of the wax to the container, as has been discussed above.

More recently, asphalt, rubber and the like have been packaged in multiwall paper bags, or cartons, whose inner walls are coated vwith powdered materials such as clay, or with soapy or oily substances. Containers of this class are not entirely satisfactory, however, inasmuch as clean release of the container from the packaged material fr'equently, is not obtained. As a consequence, contamination of the latter with the coating substances occurs. Accordingly, it is the general object of this invention to provide for use in packaging tacky materials such as wax, asphalt and rubber, an improved and highly effective container which can be removed rapidly and easily fromthe tacky contents without contamination thereof.

We have discovered that a container which overcomes the deficiencies of the prior art containers, and which meets the foregoing requirements for containers of this class, comprises broadly a base member, and bonded to the inner surface of the base member a release coating comprising one or more members of a group of synthetic elastomers which are unique in having the common propy erty of clean and rapid release from tacky materials.

.butadiene vinyl terpolymers, mixtures of acrylic and vinyl polymers, and mixtures of acrylic-butadiene copolymers and vinyl polymers. These various elastomers may be used singly or in combination with each other. When applied to the inner surfaces of suitable base members, they form containers into which wax, asphalt, rubber, and like materials may be placed, handled and transported under all the usual atmospheric conditions of temperature and humidity without hazard of adherence of the container to the tacky contents.

Considering the foregoing in greater detail and with particular reference to the drawings, wherein is presented a fragmentary sectional view of a piece of a tacky object packaged in the herein described container:

As is evident from the drawing, the container of our invention comprises a base member to the inner surface of whichis adherently united a release coating, the resulting container then being used to hold a quantity of wax, asphalt, rubber or other tacky material.

The base member maybe fabricated from any suitable material such as cloth, wood, glass, metal, cardboard, or

paper in the form of bags, boxes, cartons, or other suitable shapes. Preferably, however, the base member comprises a paper bag which may be used per se or as a liner for base members of other classes. Such a bag may be employed to advantage as the innermost of several nesting bags, providing a multiwall bag such as has been found particularly well suited for use in transporting and storing tackymaterials.

When a paper bag or other paper packaging unit is "employed, as the base member, it should be made of the coating. Also it should have a high finish, good a strong paper, preferably of unbleached kraft pulp. It should be well-sizedv to prevent excessive penetration of purpose. nate, the sodium salt of polyacrylic acid, casein, methyl ccllulose and' the like. 'Theseand other thickening agents,

tear resistaneepandjgood resistance to delamination. If

desired, its physical properties maybe improved by' the inclusion of wet-strength resins, starch, or other conventional pulp additives. h

The basis weight of the paper 'sheet employed. for coating. with an elasto'rrieric composition asdcscribed herein may vary ov'er"ajbroad'range, ifle. from about'30 lbs/ream.(3000 square'feetlto about 300155. per'rearn, which is' the value employed for heavy p aperj boards. It

is preferred, howeven to use a paper" 'sheethaving' a'basis fweight'offfrorn 35 "to'60 .pouridsrier'ram when the sheetis toibe used as aliner' for 'containers, as an inner ply for 'multiwali bags,or .for'conver'sion'into a single ply. bag. The inncrsurfaces of these and other suitable ofthe' class consisting of'the'acrylic polymers, the chloroprene polymers, the arcylic-butadiene copolymers, the

lbutadien'e-styrene copolymers, the acrylic-butadiene-vinyl terpolymers, mixturesof'acrylic andl'vinyl polymers, and

mixtures of acrylic-butadiene copolymers and vinyl p'olyer'alk'yl methacrylates. It alsoin cludes blendsand copolymers of theabove enumerated polymeric substances.

By chloroprene polymers is meant theproduct resulting fromthe'polymerization of Z-chIoro-lJ-butadiene,

and itshomologs. v

The term butadiene'polymer 'refers'to'polymerized butadiene, aswell astothe homologs and analogs of this material containing'the butadiene nucleus and having rubber-like physical "properties.

By vinyl polymer is rneant the-class of polymeric compounds containing the vinyl radical such as styrene, vinyl acetate, vinyl-chloride and vinyl chlo'ride acetate, vinylidene chloride, and mixtures thereof.

By aerylic butadiene copolymer. is "meant the 'copolymer resulting from the polymerization "of an acrylic "compound such as islisted "above with butadiene.

By butadiene-styrene -copolymer" is meantxthe polymeric substance resulting 'from the copolymerizationof butadicne and styrene.

By acrylic-butadiene-vinyl*terpolymerf is mea'ntythe elastomer resulting 'from. the copolymerization of an acrylic compound with butadieneand 'a vinylcompound.

The foregoing polymeric materials may be used'singly or in combination with'each other.- -Mixtures-in any desired proportion of the "acrylic 'and -vinyl"polyr'ners,

and of the acrylic-butadiene,copolymerswithdhe vinyl polymers, are particularly suitable. They should'be "employed, however, in the form of emulsions, or ofsolutions in suitable organic-solvents. Suitable" solvents foifthis i used singly or in admixture with each other, maybe added to the composition as required to raise the viscosity of the composition to the desired value.

For further adjustment of viscosity, water or other liquid media may be incorporated in the compositions. By this means a close control of viscosity may be achieved.

Afteradjustment of the viscosity of the polym ericcoating composition to the selected value, it may be applied to. the paper bagor other base member by anyconventional method such as spraying, brushing, spreading or roll coating. Care should be taken, however, to insure that the coatingbe applied in such a manner as to produce a continuous film of uniform weight. Also, it should e applied in unit amounts suliicient to make possible an easy and clean release of the coated surface from the tacky material to be packaged. In general, an application of from about'3. to 3O pounds (dry basis), preferably-from 6m pounds (dry basis),ofcoating per 3000 square feet of base member surface may be applied.

Coating compositions suitable for use as release coatings in the preparation ofthe'herein described containers are illustrate'dfurther in-the following examples, wherein acr.ylate and acrylonitrile'in the .form of an aqueous purpose comprise, for example, the ketonefsolventssuch as acetone or methyl ethyl ketone; or the ester solvents including methyl acetate, ethyl acetate, or the 'like.

The elastomersused in formulating these emulsions or solutions should be advanced .to a viscosity level at which they are capable of forming'a flexible-solid film when deposited upon asurface. In general, a viscosity 7 range of between'about and 100,000 centipoises at 25 C. is suitable. A preferred viscosity range is'be tween about 125 and 5000centipoises, at 25 C. y

In certain instances it vmay be desirable to mix "a thickening agent with the elastomeric coating composition in order to increase theviscosity to a valucwhich is particularly suitable fora selected c'oating operation. Any compatible thickening agent inay 'be used for this Examples are alpha protein, ammonium algiparts are given as partsby weight (solids basis).

Example] p Parts Acrylic polymer Thickening agent 1 The: acrylic polymer used was a blend of ethyl methe'rnulsidn containing 50% solids and having a viscosity of 15-20 centipoises at 25"C. and a specific gravity of 1.05. 'The thickener was a sodium salt of polyacrylic acid, supplied by the'Rohm andHaas Company under -the trade-name Acrysol GS. t

The thickener was dissolved in water to form a solution-of about 15% .solids and the solution was then mixed at room temperature with the polymeric emulsion until a homogeneous mixture was obtained. The viscosity of the final mixture .at 25 C. was 200 centipoises.

V jExainpleZ H Parts Acrylic polymers; .100 r Thickener 0.5

Theaerylic polymer used was a blend of high alkyl acryheestersin the form of an aqueous emulsion containing 40% solids, having a viscosity of 10-l5 centiporses at25f C and a specific gravity of 1.04. The thickener was ammonium alginate in powdered form. The alginate was dispersed in water to form a dispersion containing 5% solids, and mixedwith-the polymer emulsion until a homogenous mixture was produced. The viseosity of the final'composition was 450 centipoises.

Example3 t V p 'Parts Acryh'c-butadrene. 'copolymer 100' Thickener I a v 3 The acrylic butadiene copolymer was prepared by poly- -nrerizing together 33 parts acrylonitrile and 67 parts butadlene until a flexible film forming resin was produced. Thrs copolymeric resin then was employed in the form of an aqueous emulsion containing 40-45% solids, having a'viscos'ity of"1030 centipoises at 25 C. and a It is, manufactured and sold specific "gravity of 10.98. "by the Goodyear Tire/and Rubber Company of Akron Ohio, under the trade-name Chemigum 245 CHS. The thickener, A'crysol GS, was prepared and added to the emulsion in theirnanner described in Example 1. V

The viscosity of .finaljmixture was 380 centipoises.

' fEx ample 4 q I Parts A'cryl c polymer- 50 variresome The acrylic, polymer was the same high alkyl acrylic ester polymer described in Example 2. The vinyl type polymer was polyvinyl acetate in the form of an aqueous emulsion containingv 55% solids, and having a viscosity of 800-1000 centipoises at 25 C. and a specific gravity of 1.2. It was supplied by E. I. du Pont de Nemours, Wilmington, Delaware, under the trade-name Elvacet 81-900.

Both compounds were mixed together with stirring until a homogeneous mixture was obtained. The viscosity ofthe resulting composition was 5 centipoises, which was suitable for coating application by a kiss-roll method without mixing in a thickener.

Example Parts Acrylic monomer 32.5 Vinyl-type monomer 35.0 Butadiene-type monomer Thickener The three monomeric components of this composition were used as a terpolymer of acrylonitrile-styrene-butadiene in the form of an aqueous emulsion, containing 35-37% solids, having a viscosityof 11-14 centipoises at 25 C., and a specific gravity 1.02, supplied by Naugatuck Chemical, Naugatuck, Connecticut, under the trade-name Kralastic 4100-E.

The thickener was alpha-protein (isolated soya protein) solution, prepared by adding 4 parts of the protein to sutficient water to form a 15% aqueous slurry, heating the slurry to 38 C., adding 0.5 part of 28% ammonium hydroxide solution to solubilize the protein, and mixing until the protein was dissolved. The protein solution then was added to and mixed with the polymeric emulsion until a uniform mixture was obtained. The viscosity of the final mixture was 2000 centipoises.

Example 6 Parts Acrylic-butadiene type copolymer 45- Vinyl-type polymer 55 Thickener 1.5

The elastomeric components of this composition were used as a mixture of polyvinyl chloride with acrylonitrilebutadiene copolymer which had been produced by copolymerizing 15 parts of acrylonitrile With 30 parts of butadiene. The composition was in the form of an aqueous latex emulsion containing 48-50% solids, and having a viscosity of -15 centipoises at 25 C., and a specific gravity 1.09. It was marketed by B. F. Goodrich Chemical Company, Akron, Ohio, under the trade-name Geon 552. The thickener, Acrysol GS, was prepared and mixed with the emulsion in the manner described in Example 1. The viscosity of the final mixture was 145 centipoises.

Example 7 Parts Butadiene-styrene copolymer 100 Thickener -l 5 The butadiene-styrene copolymer, which had been produced by copolymerizing 40 parts of butadiene with 60 parts of styrene, was used in the form of an aqueous emulsion containing 48% solids and having a viscosity of 11 centipoises at 25 C. and a specific gravity of 1.01. It was supplied by the Dow Chemical Co., Midland, Michigan, under the trade-name Dow 512R.

The thickener, alpha-protein solution, prepared in the same manner as described in Example 4, was addedto and mixed with the polymeric emulsion until a uniform mixture was obtained. The viscosity of the final mixture was 370 centipoises.

Example 8 Parts Chloroprene polymer 100 Thickener 3 The chloroprene polymer was an aqueous emulsion of Neoprene latex Type 736, containing 34-36% solids, having a viscosity of 5 centipoises at 25 C. and a specific gravity of 1.05. It was manufactured by E. I. du Pont de Nemours, Wilmington, Delaware.

The thickener, alpha-protein solution, prepared in the same manner as described in Example 4, was mixed with 10 parts of extremely fine particle size zinc oxide, 3' parts of an anti-oxidant (symmetrical di-beta-naphthyl-paraphenylenediamine), and 0.5 part of a dispersing agent (water-soluble, polymerized sodium alkyl aryl sulfonate).

The above ingredients were mixed together in aballmill, the resulting'mixture added to the polymeric emulsion, and stirred until a uniform product was obtained. The viscosity of the final coating composition was centipoises.

All of the foregoing exemplary coating compositions are suitable for use in coating paper bags or other base members in accordance with the method described herein. In each case, they may conveniently be applied to one side of a paper web made from unbleached kraft paper and having a basis weight of 47 pounds per ream using any conventional coating apparatus. The coating may be dried to produce a continuous film which is firmly bonded to the base.

The product then is ready for fabrication into a container of the desired class, such as a multi-wall paper bag, a liner for a wood, metal or glass carton, or a single wall bag. In all of these applications, of course, the

, coated sheet is employed as the inner ply, with the coated surface being exposed to the materials to be packaged.

Wax, asphalt, rubber, or any other tacky material may be packaged successfully in the containers by filling the same with the molten material. The top of the container then is closed and the material allowed to harden. It then is ready for storage or shipment.

Because of the desirable properties of the coating the contents of the container do not penetrate or bleed through the container walls. Also, the container may be stripped off or otherwise removed rapidly and easily without adherence of the tacky contents to its side walls. Accordingly when the material is ready for use, it is available in a pure condition, uncontaminated by adhering fragments of the container.

It is to be understood that many modifications of the above embodiments of this invention will readily occur to those skilled in the art. All such modifications are intended to be included within the scope of this invention as defined in the appended claims.

We claim:

1. A package of Wax comprising wax and a container for said wax, said container comprising a base member and intermediate said base member and said wax a coating adherently united to the surface of said base member, the coating consisting essentially of at least one member of the group of synthetic elastomers consisting of the acrylic polymers, the chloroprene polymers, the acrylicbutadiene copolymers, the butadiene-styrene copolymers, the acrylic-butadiene-vinyl terpolymers, the mixtures of the acrylic and vinyl polymers, and mixtures of the acrylicbutadiene copolymers and the vinyl polymers; the amount of coating employed being sufiicient to insure easy and clean release of the container from the Wax.

2. A package according to claim 1 wherein the coating consists essentially of an acrylic polymer.

3. A package according to claim 1 wherein the coating consists essentially of a blend of ethyl methacrylate and acrylonitrile.

4. A package according to claim 1 wherein the coating consists essentially of an acrylic-butadiene copolymer.

5. A package according to claim 1 wherein the coating consists essentially of a copolymer of acrylonitrile and butadiene.

6. .A package according to claim 1 wherein the coating consists essentially of a mixture of acrylic and vinyl polymers.

,7. Apackageaccording to claim l wherein the coating consists essentially of .a blend of higher alkyl acrylic esters and polyvinyl acetate.

8. A package according to claim. lwherein the coating consists essentially of an acrylic-butadiene-vinyl' terpolymer.

, 9., A: package according to claimyl Whereimthecoating .consists essentially of an acrylonitrile-butadiene-styrene 'terpolymer.

10. A package according to claim 1 wherein thecoating consists essentially, of a mixture of an acrylic-butadiene copolymer and a'vinyl polymer.

11. A package according to claim 1 wherein the coating consists essentially of an acrylonitrile-butadiene copolymer and polyvinyl chloride.

12. A packageofwaxcomprising wax and a container for said wax, said container comprising a fibrous cel- -lu1osic base member and a coating bonded to the inner surface thereof, the coating consisting essentially of at least one synthetic ,elastomer selected from the group consisting of the acrylic polymers, the chloroprene polymers, the acrylic-butadiene-copolymers, the butadienestyrene copolyme'rs, the acrylic-butadiene-vinyl terpolymers, mixtures of the acrylic and vinyl polymers, and

t z s 4 mixtures of the acrylic-butadiene copolymers and the vinyl polymers, the dry weight of the coating being from "3 to 30 pounds per 3000 square feetof container surface.

f 135A package of wax comprising wax and a container for said-wax, said containercomprising a multiwall paper .bag, the inside surface of the'inner ply of the bag having firmly'united thereto a coating consisting essentiallyof at least one synthetic elastomer selected from the group consisting of acrylicpolymers, the chloroprenc polymers, the acrylic-butadiene-copolymers, the butadiene-styrene releasable from the Wax.

'14. The wax package of claim 13 wherein thelcoating consists essentially of an acrylic-butadiene-vinyl terpolymer.

References Cited in the file of this patent 0 UNITED STATES PATENTS 2,453,880 Vanderbilt et al. "Nov. 16, 1948 2,572,959 Sparks et al. Oct. 30, 1951 2,666,523 Ryan et al. ..'Jan. 19, 1954, 

13. A PACKAGE OF WAX COMPRISING WAX AND A CONTAINER FOR SAID WAX, SAID CONTAINER COMPRISING A MULTIWALL PAPER BAG, THE INSIDE SURFACE OF THE INNER PLY OF THE BAG HAVING FIRMLY UNITED THERETO A COATING CONSISTING ESSENTIALLY OF AT LEAST ONE SYNTHETIC ELASTOMER SELECTED FROM THE GROUP CONSISTING OF ACRYLIC POLYMERS, THE CHLOROPRENE POLYMERS, THE ACRYLIC-BUTADIENE-COPOLYMERS, THE BUTADIENE-STYRENE COPOLYMERS, THE ACRYLIC-BUTADIENE-VINYL TERPOLYMERS, THE MIXTURES OF THE ACRYLIC AND VINYL POLYMERS, AND MIXTURES OF THE ACRYLIC BUTADIENE-COPOLYMERS AND THE VINYL POLYMERS, THE DRY WEIGHT OF THE COATING BEING FROM 6 TO 15 POUNDS PER 3000 SQUARE FEET OF INNER PLY SURFACE, AND THE 